Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$128.76	3.301%	$133.0104	$133.01	$133.00	$133.00
Purchase #2	$84.66	5.405%	$89.2359	$89.24	$89.25	$89.20
Purchase #3	$62.81	3.418%	$64.9568	$64.96	$64.95	$65.00
Purchase #4	$229.59	11.625%	$256.2798	$256.28	$256.30	$256.30
Purchase #5	$25.35	13.440%	$28.757	$28.76	$28.75	$28.80
Purchase #6	$176.55	5.276%	$185.8648	$185.86	$185.85	$185.90
Purchase #7	$221.49	10.438%	$244.6091	$244.61	$244.60	$244.60
7 purchase totals =	$929.21		$1,002.7138	$1,002.72	$1,002.70	$1,002.80